A capacitive sensor device is one example of a sensor device that is used in a touch panel or a touchpad to detect a touching operation and is known in the prior art (refer to Japanese Laid-Open Patent Publication No. 2011-14527). When a capacitive sensor device is used, a capacitor is charged so that change in its electrostatic capacitance is detectable in accordance with a touching operation. When the sensor device is powered off, the capacitor is discharged so that the potential of the capacitor is reduced to the ground (GND) level.